1. Field of the Invention
The subject invention relates to a device for preventing the overflow of a container being filled with a substance. More particularly, the subject invention is a sensor and associated circuit for regulating the fill level in a swimming pool or similar container.
2. Description of the Background Art
Several types of electronic and pressure monitors exist to regulate the level to which a container is filled with a particular substance. Many of these prior mechanisms have involved expensive and needlessly complex fabrications. The subject device has a uncomplicated sensor with a reliable control circuit which are relatively inexpensive to produce.
Specifically, disclosed in U.S. Pat. No. 3,759,286 is an apparatus for maintaining the water level within a swimming pool to a predetermined set of limits. A small ball floats within a sensor cylinder. As the water level fills the cylinder electrodes detect the height. The ball prevents overflow during activation of the pump. Since the pump is in immediate fluid linkage with the sensor, a running pump limits the usefulness of the sensor.
Related in U.S. Pat. No. 3,997,925 is another apparatus to control the water level in a swimming pool. In a stilling chamber, to quiet wave action, water enters a perforated column that contains two level detecting electrodes and a ground electrode. The water is maintained at predetermined heights. A water release system very similar to a traditional lever arm toilet fill system is incorporated into one embodiment of the device.
A pressure activated liquid level control apparatus is described in U.S. Pat. No. 4,014,052. The device is positioned over the edge of a tank to permit the device's housing to be in and out of the tank. Several passageway are interactively connected to regulate the liquid level within the tank.
U.S. Pat. No. 4,133,059 presents an automated surge weir and rim skimming gutter flow control system for use with a swimming pool. A plurality of electrode gutter sensors helps adjust the level to a desired position. Connected to the chamber that holds the gutter sensors is a complex surge weir to damp wave action.
Control circuitry for water level control within a pool is disclosed in U.S. Pat. No. 4,380,091. A multi-level detecting sensor is coupled to a sophisticated controlling circuit having internal oscillators.
Furnished in U.S. Pat. No. 4,612,949 is an apparatus for controlling the liquid level in a fluid reservoir. The sensor is either used within a conventional pool skimmer or secured to the wall of the reservoir. A perforated cylinder with a threaded central electrode serves as the basic probe construction. Found in the circuit electronics are logic blocks for determining the level of the liquid and ones intended to compensate for the action of waves.
Finally, U.S. Pat. Nos. 4,685,158 and 4,817,217 relate a swimming pool control system for adjusting water level. A sophisticated electronic circuit having an internal clock is employed in the system. Additionally, four electrodes are fitted within a sensor housing with one above the normal fill level, one below the normal fill level, and two located side-by-side and well below the position of either of the other two electrodes. This electrode configuration, coupled with the associated circuit, is used to limit the fill level.